cranium and orbit

What is the part position for a PA skull projection?

Prone, MSP ⟂ table, OML ⟂ IR.

Where is the CR directed for a PA skull?

Perpendicular to the nasion.

What should the petrous pyramids look like on a PA skull?

They should fill the orbits.

What structures are best seen on a PA skull?

Frontal bone, lateral cranial walls, frontal sinuses, crista galli.

What is the part position for a PA axial (Caldwell) projection?

PA, MSP centered, OML ⟂ IR.

What is the CR for a Caldwell projection?

15° caudad to the nasion.

Where should the petrous pyramids appear on a Caldwell?

In the lower one‑third of the orbits.

What structures are best seen on a Caldwell?

Frontal sinuses and anterior ethmoid sinuses.

What is the part position for an AP axial (Towne) projection?

Supine, MSP ⟂ table, OML vertical.

What is the CR for a Towne projection?

30° caudad to 1.5″ above the glabella (or 37° to IOML).

What structures are best seen on a Towne?

Occipital bone, dorsum sellae, and posterior clinoids within the foramen magnum.

What error occurs if the neck is overflexed or the angle is too large on a Towne?

The posterior arch of C1 is projected into the foramen magnum.

What is the part position for a lateral skull projection?

MSP ∥ IR, interpupillary line ⟂ IR, IOML ∥ IR.

Where is the CR directed for a lateral skull?

2″ superior to the EAM.

What structures should be superimposed on a lateral skull?

Orbital roofs, clinoid processes, and mandibular rami.

What is the part position for an SMV (submentovertical) projection?

Neck hyperextended, IOML ∥ IR, CR ⟂ IOML.

Where does the CR enter for an SMV?

MSP at the level of the sella turcica.

What structures are best seen on an SMV?

Foramina (spinosum, ovale), carotid canals, sphenoid and maxillary sinuses, dens through foramen magnum.

What indicates correct SMV positioning?

Mandibular condyles projected anterior to petrous pyramids.

What is the part position for an AP trauma skull?

Supine, MSP ⟂ table, OML ⟂ IR.

Where is the CR directed for an AP trauma skull?

Perpendicular to the nasion.

What should the petrous pyramids look like on an AP trauma skull?

They should fill the orbits.

What is the CR for an AP axial trauma skull?

15° cephalad to the nasion.

What structures are best seen on an AP axial trauma skull?

Petrous portions in the lower third of the orbits; magnified facial structures.

What is the part position for a lateral trauma skull?

Supine, dorsal decubitus, MSP ⟂ CR, interpupillary line ⟂ IR.

Where is the CR directed for a lateral trauma skull?

2″ superior and lateral to the EAM.

What pathology can a lateral trauma skull show as the only sign of a basal skull fracture?

Sphenoid sinus effusion.

How many bones form the orbital cavities?

Seven (frontal, sphenoid, ethmoid, maxilla, palatine, zygomatic, lacrimal).

What is the second most common facial fracture?

Orbital floor blowout fracture (nasal fracture is #1).

What can cause orbital edema after a blowout fracture?

Leakage of air from the adjacent maxillary sinus.

What projection best demonstrates orbital floor fractures?

Parietoacanthial (Waters).

What is the part position for the Waters projection?

PA, MSP ⟂ IR, chin extended so OML is 37° to the IR.

Where is the CR directed for Waters?

Perpendicular, exiting at the acanthion.

What structures are best seen on Waters?

Orbits, zygomas, maxillae; best single projection for facial bones.

What does the modified Waters position do?

Reduces distortion of the orbital rims (OML ≈ 55° to IR).

What is the part position for a Caldwell of the orbits?

PA, MSP centered, OML ⟂ IR.

What is the CR for a Caldwell of the orbits?

15° caudad to the nasion.

What structures are best seen on a Caldwell of the orbits?

Orbits, nasal septum, maxillae, zygomas.

Where should the petrous pyramids appear on a Caldwell?

In the lower one‑third of the orbits.

What is the part position for a lateral orbit projection?

MSP ∥ IR, interpupillary line ⟂ IR, IOML ∥ IR.

Where is the CR directed for a lateral orbit?

2″ superior to the EAM.

What structures should be superimposed on a lateral orbit?

Orbital roofs, anterior and posterior clinoids.